RosettaCodeData/Task/Bitmap-Histogram/Zkl/bitmap-histogram-2.zkl

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img:=PPM.readPPMFile("lenaGrey.ppm"); // a grey scale image
median:=histogramMedian(histogram(img));
median.println();
bw:=PPM(img.w,img.h);
// stream bytes from orginal, convert to black/white, write to new image
// each pixel is 24 bit RGB
img.data.pump(bw.data.clear(),'wrap(c){ if(c>median) 0xff else 0 });
bw.write(File("foo.ppm","wb"));